The invention relates to a universal open end ratchet wrench for tightening or loosening nuts, bolts and fasteners.
Ratchet wrenches are well known. Most ratchet wrenches utilize a socket, where the socket includes an opening formed in the shape of a specific fastener size, for example, a half inch hexagonal bolt or a 14 mm twelve point bolt head. Most ratchet wrenches are sold with a variety of sockets, each socket designed to fit a specific sized bolt or nut.
In such wrenches, the wrench includes means for securing the socket to a ratchet mechanism such that a variety of sockets may be interchangeably attached to the wrench. In recent years, ratchet wrenches and sockets have been standardized where the ratchet wrench includes a protruding shank that is 3/8 inch square and the socket has a 3/8 inch square opening to accommodate the shank. Another standard size ratchet wrench shank is 1/2 inch square with the sockets having corresponding 1/2 inch square openings.
Typically, a ratchet wrench selectively allows the socket to rotate freely in one direction, but inhibits rotation in the reverse direction so that as a bolt is tightened or loosened, the wrench does not need to be removed from the bolt.
Open end wrenches have been used for over a century. Open end wrenches typically have a U-shaped opening at one end with opposed parallel faces that are manufactured to fit one single bolt or nut size. Open end wrenches allow a technician or handyman to engage a bolt or nut when only a radial face of the bolt or nut is exposed. A drawback to an open end wrench is that the user must constantly remove the wrench from the bolt or nut and reposition the wrench in order to tighten or loosen the bolt or nut.
Also well known are open end ratchet wrenches where the ratchet wrench includes a rotatable element that has a gap formed therein to allow the wrench to slide over a bolt or nut in a manner similar to an open end wrench. Examples of such wrenches are shown in the following patents:
U.S. Pat. No. 4,479,409 to Antonius
U.S. Pat. No. 3,927,582 to Hertelendy et al.
U.S. Pat. No. 2,851,914 to Zeckzer
U.S. Pat. No. 2,712,256 to Fish
U.S. Pat. No. 2,699,082 to Viets
U.S. Pat. No. 2,691,315 to Brame
U.S. Pat. No. 2,649,823 to Markovich
U.S. Pat. No. 2,376,575 to Cronan
U.S. Pat. No. 923,942 to Brockway.
Open end ratchet wrenches have the obvious advantage over traditional open end wrenches of enabling a workman to progressively turn a nut or bolt without having to continually remove and reposition the wrench.
Problems with previous open end ratchet wrenches relate to the ratchet mechanism itself. For instance, in U.S. Pat. 2,376,575 to Cronan, the wrench includes a ratchet member having a circular shape with a gap formed therein for receiving a bolt or nut. The rotatable ratchet member has teeth formed on its outer circumference which become exposed as the ratchet member rotates. The teeth are damaged easily when left in an exposed position. The teeth may also present a safety hazard. For instance, if left exposed, the protruding teeth might puncture the skin of the user, or cause abrasions to skin in contact with them.
Another disadvantage to the Cronan '575 wrench is the inclusion of four pawls in the ratchet mechanism. The design is complicated in execution, making it difficult to assemble and repair. Further, the pawl members when worn slightly, may fail to engage the ratchet teeth on the rotatable wrench member in concert, thus making failure of one or more of the pawl members more likely.
Yet another shortcoming of the wrench disclosed in the Cronan '575 patent is that the radially extending ratchet teeth make it necessary to increase the overall diameter of the open end of the ratchet wrench. A wide diameter end is undesirable because it limits the applications where the wrench can be utilized, in particular, in small spaces where there is a finite amount of space near a bolt or nut.
A further disadvantage to the designs in the prior art lies in the likelihood that the rotatable element in the ratchet mechanism may eventually become bent or warped, in which case, rotation of the element may become limited or may be impossible altogether.